1. Field of the Invention
Embodiments of the invention described herein pertain to the field of electric motors. More particularly, but not by way of limitation, one or more embodiments of the invention enable induction motor stator windings.
2. Description of the Related Art
Electric motors convert electrical energy into mechanical energy to produce linear force or torque and are used in many applications requiring mechanical power, such as pumps, power tools, household appliances and ship propulsion units. In the case of an electric submersible pump (ESP), for example, a two-pole, three phase, squirrel cage induction motor is typically used to turn a centrifugal pump for purposes of lifting fluid to the surface of a well. These electric motors include a stationary component known as a stator, and a rotating component known as the motor shaft. In ESP applications, the stator is energized by a power source located at the well surface and connected to the stator with an electric cable. The electricity flowing through the stator windings causes a magnetic field, and the motor shaft rotates in response to the magnetic field created in the energized stator.
The stator windings are a composition of stator laminations, magnet wire and one or more types of insulating material. Thin steel laminations are pressed together inside the stator housing. These laminations contain a series of insulated slots that allow magnet wire to be strung from one end of the stator to the other in a pattern that, when energized, creates the magnetic field. The magnetic field produced by the stator windings is a function of the amount of steel laminations in the stator, the type of steel utilized in the manufacture of the laminations, the quality of the insulation on the slots and on the magnet wire, and the amount of conductive material in the magnet wire that is woven into the slots.
Typically, conventional magnet wire includes a conductive material, such as copper or aluminum, which conductor is surrounded by a layer of insulating material, such as a polyimide film or a thermoplastic with high dielectric capabilities. Magnet wire is conventionally round in cross section and is available in several different wire gauge sizes. The gauge size (or diameter of the wire), and the number of times that the wire passes through the lamination stack dictate how much conductive material in the magnet wire is included in the stator winding. The more conductive material included in the stator winding, the better the magnetic field.
FIG. 1 illustrates a cross section of a conventional stator slot that contains windings of conventional round magnet wire. As shown in FIG. 1, the conventional slot contains empty space that is not filled by insulation or the magnet wire. The “slot fill” refers to the amount of space in the lamination slots that are occupied by wire or insulating materials, and is usually expressed as a percentage of the available slot area. If the slot fill percentage is too low, the quantity of conductive material from magnet wire will be low. This may cause the magnetic field created by the motor to suffer, and the motor may not operate efficiently or fail to perform as desired. On the other hand, care must be taken not to wind the wire too tightly in the slots. Doing so can cause damage to the wire in the winding process.
Currently, induction motor stator windings are not optimized, since inserting a series of round wires into a slot leaves an excessive amount of empty space in the slot, at least a portion of which could otherwise be filled with conductive material. Therefore, there is a need for additional induction motor stator windings.